Multi layer photographic materials containing dyes having sharp green absorption



2,968,556 DYES Jan. 17, 1961 o. RIESTER MULTI LAYER PHOTOGRAPHIC MATERIALS CONTAINING HAVING SHARP GREEN ABSORPTION Filed June 12, 1956 Max.545

INVENTOR. 08/641? BIL-676E ATTORNEY-5 United States Patent MULTI LAYER PHOTOGRAPHIC MATERIALS CONTAINING DYES HAVING SHARP GREEN 5 ABSORPTION Oskar Riester, Leverkusen, Germany, assignor to Agfa Aktiengesellschaft The present invention relates to color photography and 5 more especially to color-photographic multi-layer materials containing filter dyestutfs of narrow absorption range.

It is known that the reproduction of natural colors by photographic multi-layer materials is imperfect. This is mainly due to the fact that the dyestuffs formed in said materials are such as have absorption curves which differ substantially from the path which is necessary in theory. It has, moreover, been recognized that color defects are also introduced into color exposures by the fact that the color sensitivity of the single layers of the multi-layer materials shows' deviations from the sensitivity curve which is required. As regards color exposures which are produced with color separation records, these defects can be reduced somewhat by skilled selection of color filters; however, it is often necessary for the color defects to be compensated for in a comparatively complicated manner by means of additional masks. These methods of color correction have, moreover, resulted in the introduction of other difficulties, so thatit is much more efiective for these defects to be avoided by suitable measure before they actually occur. Accordingly, it has also already been proposed thatv the defects which are introduced into the recording of the natural colors by the incorrect colour sensitivity with multilayer films should be compensated for by filter layers being incorporated between the light-sensitive layers. This can, for example, be effected in a comparatively satisfactory manner by introducing a yellow filter layer of colloidal silver between the blue-sensitive layer and the other sensitised layers, by means of which the natural sensitivity of silver halide for blue and violet light is largely excluded. When the film is processed, this yellow layer is dissolved out and thus removed. It has also already been proposed for a suitable layer to be placed between the green-sensitive and the red sensitive layers. How- 'ever, this is not successful, because it is extremely difficult to produce such a red-dyed layers so that its colouring is subsequently completely removed in the necessary manner. It is true that a similar colloidal silver of red appearance exists which could be bleached out, but this shows such a high general absorption that the sensitivity of the lowermost red-sensitive layer is too greatly impaired. It has further been proposed to embed organic dyestuffs in an intermediate layer, whereby the undesirable secondary sensitivity of the red-sensitive layer should be prevented. However, it has been found that it is on the one hand very diflicult to develop such dyestuffs which show a sufiicient absorption and-which on the other hand areso completely bleachedihat no subsequent residualcolour formations are produced. Furthermore, the new difliculty arises that these dyestufis had at'the sam time to be resistant-to difi aqmbecam otherwise they would migrate during casting or during the normal layer formation into the other layers and prevent sensitisation in these layers owing to their de sensisting properties, or they simply acted as filter dyestufis and reduced the green-sensitivity, so that it was no longer possible in this layer to effect a recording with the necessary sensitivity.

It has now been found that a substantial improvement in the colour reproduction can be produced with multilayer materials by using filter layers containing one or more dyestuffs which are present in a diffusion-resisting and highly associated form (resistant to dissociation) and produce absorption bands which are so positioned that the undesirable green sensitivity in the sub-layer sensitised for red can be substantially reduced.

Dyestuffs which transform surprisingly readily into a special and more highly associated form, whereby they simultaneously become resistant to diffusion and assume remarkably sharp absorption, are for example rhodacyanines, benzimidazol carbocyanines, and benzoxo- 'carbocyanines, which latter preferably carry phenyl radicals in the 6-position of the benzoxazole ring or benzene rings anellated in 5 and 6 position. The preparation of the rhodacyanines is disclosed in German Patents Number 890,249 and Number 930,275. The preparations of the other dyestuffs are respectively disclosed in German Patent Nos. 714,764, 733,026, 929,080, and 936,644 as well as in US. Patent No. 2,739,149.

According to the statement made above, the resistance to diffusion in the first place makes it possible for them to be used at all for the desired selective exclusion of the incorrect sensitivity. In the second place, the particularly high selectivity which is produced by the association' of these dyestuffs renders it possible for the redsensitivity of the lowermost layer to be satisfactorily ob tained, this being particularly valuable in order to obtain the high general sensitivity which is absolutely necessary. This selectivity is even so great that it is scarcely any longer necessary to remove these dyestuffs in the subsequent photographic processing, but they even have a favourable effect in the copying process, in that they produce further selectivity due to their filtering effect on the positive material. This does in fact result in an intensification of the selective sensitivity of the sensitisation of the green-sensitive part of the positive film or paper layer, which is ina position to effect a further improvement in the final colour reproduction. The position of the absorption maximum must only be so chosen that the sensitisation maximum of the green-sensitive layer is not of the same density as the positive material, so that the exposure time is not increased to too high a degree in the production of the colour positive in this case, due to the filtering action being too strong. A moderate weakening is quite unimportant and it can in certain circumstances often be desirable, if the green sens-itisation of the positive material is particularly high.

Example 1 In the accompanying drawing, Figure 1 :shows a multilayer material for negative exposures, in which are indicated the sensitivity ranges of the three light-sensitive layers 1, 2, 3 and also the absorption ranges of the yellow filter layer 4 and the green filter layer 5. Figure 2 shows a multi-layer material which is suitable for the production of copies from negative colour images on materials according to Figure l. The sensitivity ranges of the lightsensitive layers, 6, 7, 8 and the. absorption range of the yellow filter layer 9 are shown in Figure 2.

v 3 Suitable dyestuffs for the filter layer 5 are the rhoda- 'cyanines of the formulae:

In the green filter layer, there are employed two dyestuffs, theabsorption maxima of which are such that they are disposed on both-sides of the sensitisation maximum of =the-green-sensitive layer of the positive copying film. Such a material is "shown 'in Figure 3. The sensitivity ranges of the light-sensitive layers 10, ll, '12 and the absor'p'tion ranges of the yellow filter layer -13 andthe green filter layer 14 are shown in this figure.

The associated positive is the same as indicated in Example 1, it being of course also possible for the layer sequence to be changed, that is to say, the blue-sensitive layer can-be followed by a yellow filter layer and then by the-red-sensitive layer, the green sensitive layer only following at the last layer.

The green filter layer has added thereto mixtures rhodacyanines of the following formulae:

provides a sharp absolute maximum at 540 m (absorp tion of small width at half of maxmum intensity). If a wetting agent, such as saponin, is additionally used, the absolute maximum is at 525 mp.

The dyestuff of the formula:

(XIII) provides a narrow absorption; its maximum is 564 mp The dyestuii of the formula:

is introduced into gelatine and shows a very sharp absorption at a maximum of 575 III .4. The dyestuff can be added to the gelatine as a solution in methanol or in dilute acetic acid; in the latter case the gelatine is adjusted neutral or weakly alkaline by addition of organic or inorganic alkaline. In similar manner the dyestufi of the formula:

CH3 N 11:

:@ \CCH=CH-CH=C/ I) I- or Ilw/ provides a narrow absorption at a maximum of 585 mg. The above two dyestuffs can be removed even after the developing and fixing process by after-treatment With dilute acids or by the interaction of any treatment solutions usually employed in photographic processes, if these treatment solutions show an acid reaction.

The constitutions indicated can of course be replaced by the mesomeric forms; they are merely to be interpreted as recording formulae and do not represent any limitation. The dyestuffs can be introduced into a layer which consists wholly or in part of gelatine, polyvinyl alcohol, starch, dextrin, etc., and also of mixtures of such layerforrning substances, which in their turn can .be mixed with substances for varying the viscosity, such as polyacrylic acids, copolymers of maleic acid and styrene etc. The dyestuffs can be introduced in the form of their solutions in an organic solvent, such as for example methanol, or even inwater, or can be supplied by the filter layer being placed in a bath.

Moreover, the solubility thereof may be increased by adding organic or inorganic salts.

What I claim is:

l. A multi-layer emulsion combination for making multi-color photographs, said combination having a support, a layer of red-sensitive silver halide emulsion on said support, a filter layer having sharp green absorption over said emulsion, a layer of green-sensitive silver halide emulsion over the green filter layer, a yellow filter layer "16 over said layer of green-sensitive emulsion, and a layer of blue-sensitive silver halide emulsion over the yellow filter layer, said sharp green absorption being producted by dyestufi selected from the class consisting of the formulae 0411s SO:- I

0 (I) CCH=C Na N Y a r a 432115 CH: CH: l

1 CH: HC-GH I HC-CH; 803 1 2. The combination of claim Tin which the green filter 8 layer contains two of the specified dyestuffs that have sharp absorptions in different portions of the green band.

References Cited'ih the file of this patent UNITED STATES PATENTS 1,878,961 Mees Sept. '20, 1932 2,112,226 Baldsiefen et a1 Mar. 29, 1938 2,231,659 Brooker et a1 Feb. 11, 1941 (10 2,628,901 Duerr Feb. 17, 1953 2,739,149 Van'Lare Mar. 20, 1956 UNITED STATES PATEN'I OFFICE CERTIFICATION OF CORRECTION Patent No. 2,968,556 January 17 1961 Oskar Riester It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 6, lines 24 to 34: the formula should appear as shown below instead of as in the patent:

same column 6, lines 46 to 54 the formula should appear as shown below instead of as in the patent:

Signed and sealed this 8th day of May 1962,

(SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents 

1. A MULTI-LAYER EMULSION COMBINATION FOR MAKING MULTI-COLOR PHOTOGRAPHS, SAID COMBINATION HAVING A SUPPORT, A LAYER OF RED-SENSITIVE SILVER HALIDE EMULSION ON SAID SUPPORT, A FILTER LAYER HAVING SHARP GREEN ABSORPTION OVER SAID EMULSION, A LAYER OF GREEN-SENSITIVE SILVER HALIDE EMULSION OVER THE GREEN FILTER LAYER, A YELLOW FILTER LAYER OVER SAID LAYER OF GREEN-SENSITIVE EMULSION, AND A LAYER OF BLUE-SENSITIVE SILVER HALIDE EMULSION OVER THE YELLOW FILTER 